Myerson says Windows 10 targets three pillars: "mobility of the experience," trust and "the right interaction at the right time," hinting the platform can be controlled by mouse, touch or even gaze.

Among the new features is the introduction of a successor to the Internet Explorer Web browser, dubbed Project Spartan. The browser, which will work across multiple devices, includes a note-taking feature for annotating webpages, a reading mode and built-in support for PDF files.

The Start menu appears to be a hybrid of the classic Windows PC interface and the tile-based presentation of applications, allowing users to go full screen with the Start menu for more information.

Microsoft will also add Cortana, the personal digital assistant users communicate with through voice, to PCs running Windows 10. Users will be able to ask Cortana to pull up PowerPoint slides, send e-mails or search for photos and other information.

Microsoft will integrate Skype across all devices, and include Office programs Word, Excel and PowerPoint on all Windows 10 phones and tablets. It will also feature an Xbox app where users will find their games or follow the activity of friends.

All owners of devices running Windows 7, Windows 8 or 8.1 will get a free upgrade to Windows 10 for the first year.

"We want to move from people needing Windows, to choosing Windows, to loving Windows," said Microsoft CEO Satya Nadella.

While PCs and mobile devices dominated the event, Microsoft offered an incredible glimpse into the future with a jump into holographic computing. The company introduced the HoloLens, a virtual reality style headset that allows its users to view holograms in the real world. Demos showed users watching Netflix programs on a virtual screen, or manipulating three-dimensional images.

Windows 10 is the first significant upgrade to the platform since the arrival of Satya Nadella as CEO last year. During his tenure, Nadella has made a strong push toward mobile, enterprise and the cloud as well as thrown support toward the company's popular Xbox video game brand.

The introduction of Windows 10 is the first step in Microsoft realizing Nadella's vision, says FBR Capital Markets analyst Daniel Ives. "This is about Nadella leading Microsoft into its next stage of growth away from the PC and towards a cloud, virtualized world which can connect all devices on one platform."